In a conventional device, a hollow cylindrical part is provided in a pump housing (called a body or a base) of the pump as a first member. A cylinder (called a plunger support member, a plunger slide tube, or a cylindrical member) as a second member is made to fit the hollow cylindrical part. The pressurizing chamber that pressurizes the fuel is formed by closing the open end of the cylinder using a seal plate. A reciprocation plunger, having a point that goes into and out from the pressurizing chamber, is supported by this second member so as to go in and out.
Such a conventional device, for instance, is proposed as a high-pressure fuel feed pump for an internal combustion engine by Japanese Laid-Open Patent Application No. 11-82236.
This document describes a high-pressure fuel feed pump that can decrease man-hour requirements, while ruining neither wear and abrasion resistance nor liquid seal properties, by making the second member, which keeps the slidable plunger wear and abrasion resistant, and the first member, into which the second member is inserted, of wear and abrasion resistant material like an aluminum alloy.
However, in this prior art, the pressurizing chamber and the low-pressure chamber are sealed by pressing a seal plate, provided at the open end of the cylinder, against the cylinder end surface. Further, the first member and the second member are almost contacted in the opening area of the periphery of the second member. Therefore, a difference in heat deformation amounts is caused according to the difference in the thermal expansion coefficients between both members. As a result, the cylinder receives stress and deforms locally when both members expand due to the effect of heat, and the plunger wears the cylinder. Further, the space between the plunger and the cylinder wall surface is about five microns. An average thermal expansion coefficient of the aluminum alloy member is 23×10−6. Moreover, an average thermal expansion coefficient of an iron system member is 10×10−6 for steel, and 17×10−6 for SUS. If the diameter (inside diameter or outside diameter) is 30Φ, thermal expansions of 7 microns, 3 microns, and 5 microns are caused, respectively, because the amount of thermal expansion is obtained by diameter×thermal expansion coefficient×temperature variation difference. These thermal expansions act on the outside wall of the cylinder, and cause deformation of the cylinder.
Moreover, because it is necessary to assemble the first and second members so that they do not come off, and with many seal rings installed between the first member and the second member, assembly of the first member and the second member is difficult, and not practicable.
Further, the plunger in the above-mentioned prior art document might be referred to as a piston or a reciprocating rod in other documents. The plunger of the present invention is the same as these members. Of course, it is possible to functionally refer to the element by which the fluid is pressurized. Therefore, both a plunger with a rod shape or another pressurizing element having the function of compressing the fluid can be used.
Both an element with the rod shape described and also an element of a shape having a pressurizing function that is not described are included in the term “pressurizing element” in this application.